There are a billion 1911's out there, and the ones that are poor quality generally don't survive in stores long. Basically, spend your money on what has the options you want, for the price you want. Or at least find what looks good to you then do a half hour of research on it.
As for AR's, its kind of the same deal. Colts are very pricey, and some of their models use non standard size roll pins to hold everything together in the lower. They were trying to make it so that you couldn't use mil spec parts in civilian guns but all the other manufacturer's ignored the idea. I don't see any reason to buy a Colt. Once again, look around for what has the options you like for the price you want, or you can go the build it yourself route. If this is the case, pick up a bare receiver wherever, a good lower parts kit, a nice stock, and figure out what style upper you want.